[Qemu-devel] [PATCH v2 03/20] 9p: xattr: Fix crash due to free of uninitialized value

[Keno Fischer]

If the size returned from llistxattr is 0, we skipped the malloc
call, leaving xattr.value uninitialized. However, this value is
later passed to `g_free` without any further checks, causing an
error. Fix that by always calling g_malloc unconditionally. If
`size` is 0, it will return a pointer that is safe to pass to g_free,
likely NULL.

Signed-off-by: Keno Fischer <address@hidden>
---

Changes since v1: New patch

 hw/9pfs/9p.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index d74302d..b80db65 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -3256,8 +3256,8 @@ static void coroutine_fn v9fs_xattrwalk(void *opaque)
         xattr_fidp->fs.xattr.len = size;
         xattr_fidp->fid_type = P9_FID_XATTR;
         xattr_fidp->fs.xattr.xattrwalk_fid = true;
+        xattr_fidp->fs.xattr.value = g_malloc0(size);
         if (size) {
-            xattr_fidp->fs.xattr.value = g_malloc0(size);
             err = v9fs_co_llistxattr(pdu, &xattr_fidp->path,
                                      xattr_fidp->fs.xattr.value,
                                      xattr_fidp->fs.xattr.len);
-- 
2.8.1